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/*
Copyright 2022 Gabriel Jensen.
This Source Code Form is subject to the terms of the Mozilla Public License, v. 2.0.
If a copy of the MPL was not distributed with this file, You can obtain one at https://mozilla.org/MPL/2.0/.
*/
#include <zap/priv.h>
.globl zap_strlen
zap_strlen:
/*
char const * str
*/
#if defined(__amd64__)
# rax: Address of the current character.
# rdx: Current character.
movq %rdi,%rax
# Iterate over the string:
.loop:
# Move the character into a register:
movb (%rax),%dl
# Check if we have reached the null-terminator:
testb %dl,%dl
jz .done # If so, we are done.
# Continue to the next character:
incq %rax
jmp .loop
# Done:
.done:
# Get the length:
subq %rdi,%rax
ret
#endif
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